The parasympathetic nervous system exerts the major control over the excretory and sexual reflexes. Understanding the morphological and neurophysiological bases of these reflexes is essential to the treatment of not only the great number of spinal cord injured patients, many of whom may die from complications related to the lack of control over their micturition reflexes, but also of aged people suffering problems of incontinence. The research proposed here is designed to study the morphology of bladder and colon preganglionic neurons and related interneurons in the sacral parasympathetic nucleus in the spinal cord. These neurons will be identified neurophysiologically, injected intracellularly with HRP, and will then be examined at both the light microscopic (LM) and the electron microscopic (EM) levels. Their morphologies will be compared and correlated with their different roles in the excretory reflexes. This technique offers five advantages over present methods: First, intracellular methods fill and reveal more completely the neurites of a nerve cell than retrograde HRP methods. Second, they will permit an examination of individual neurons whereas the retrograde methods produce only multiple labeling. Third, they provide a positive identification of the neurons which Golgi methods do not. Fourth, intracellular methods will permit study of these neurons, particularly of their distal dendrites and synaptic terminals, at the EM level, whereas retrograde methods will not. Finally, this method offers the advantage that specific neurophysiological characteristics may be associated with their morphology. The basic information obtained will be directly relevant to further understanding of normal function and essential to any subsequent attempt at unraveling the alterations in function that result from spinal cord injury.